Signal measuring system



Feb. 6, 1940.

J. J. SCHLUTER SIGNAL MEASURING SYSTEM Filqd Sept. 8, 1938 INVENTOR J /m(Isa/km ATTORNEY Patented Feb. 6, 1940 mire, STATES PATENT O EN 4Claims.(cine-475.1)

. i This invention "relates'to electrical signaling systems. Moreparticularly this invention relates to'electrical systems for indicatingto the speaker or operator the level of speech or other currents.

'5 When speech or other energy is impressed upon the telephonetransmitter of a telephone sub.- .scribers set'it is :difiicu'lt andoften impossible for thespeaker or operator to determine whether the'levelof the impressed energy issufiicient for io good' transmission.:Two factors largely determine whether or not theimpressed energy issufficient for good transmission to the distant end *of the circuit.These two factors are (l) the dis H tance between the speakers lips andthe teleili phonetransmitter and"(2) the tone or level of .the voiceused... 1 1 i 1 1 .Speechforother' energy of loud-tone or high levelneed notbe impressed as closely to the telephone transmitter as energyof lower tone or Q level to'producethe same electrical effects. A :verylow toneor signal level will necessarily have to be impressed quiteclosely to the telephone transmitter to beeifectively transmitted to thedistant station. If a low tone is produced a substantial distance fromthe. transmitter it may of course be so attenuated bythe circuit as tobe. practically T inaudible at the distant end. The determination of theproper tone or level and/or the proper 'distance between the speakerslips and the. telephone transmitter is" of importance to. the efficientuse of signaling systems employed for telephone transmission.

*It is therefore one'of the objects of this invention to indicateinstantly to the subscriberor operator the approximate level of speechor other signal energy impressed upon atelephone transmitter which, for:example, may be part of a telephone 'subscribers set. I It is a furtherobject of this invention to in- 40 dicate instantly to the speaker oroperator whether the level of speech or other signal energy issufficient for good transmission.

It is a still further object of this invention toindicateapproiiimatelywhat the level of the energy impressed upon thetransmitter may be when thesource of the energy is positioned atdifferent distances from the transmitter.

These. and other objects and features of the which may bea part of atelephone subsc'rib'ers set. This transmitter may be connected to theprimary windingof a transformer T1, the connection being'establishedthrough a double-pole -single-throw switch S1 and through the upper 5'blade of 'a double-pole. single-throw switch S2.

The secondary winding of the'transformer T1 7 is connectedas part of thegrid circuit of an amplifier. tube V1 which will be referred to againhereinafter. I 110 'Anelectrical buzzer Y of any Well-knowntype,

having a source ofxcurrent for its operation as .shown, may bepositioned directly in-front of the transmitter TR so that soundsproduced by the I buzzer will become impressed upon the transmit l5 terTR and then transmitted tothe grid circuit of the amplifier tube V1. Itwill hence be apparent that upon closureof the switches Srand 'Sz,voiceenergy or'the buzzer energy may beimpressed'nponthe transmitter TRahdthen am- 20 'plified, the amplifiedenergy being utilized forobtaining, an indicationof thelevel'of the impressed energy as will bedescribed more. fully hereinafter. l 1.

- The apparatus' for determining the level of the 25 energy impressedupon the grid circuit of the tube V1 includesa' generator of alternatingcurrent designated G which may be a, -cycle alternatingcurrentgenerator'of 100 or 115 volts which may be connected by i a double-polesingle-throw switch Syand through the lower blade of a similardouble-pole single-throw switch S4 to the primary windings oftransformers T2 and T3, these primary windings being connected inparallel re lationship. When both of the switches S3 and S4 are closed,the lamp L0 will be lighted and The secondary winding. of thetransformerTa 40 isconnected to the filament or heater of the tube 'V1aswell'as to the filament of the tube V2, the

two filaments being aranged in parallel relationship. The secondarywinding of the transformer Ta will be utilizedtoheat the filaments oflamps L1, Lz'or Ls'ina manner to be described more. fully hereinafter. Ii l l A Theamplifier tube V1 is of the heater type, the cathode of whichis in circuit with a resistor 210,;

the secondary windingiof the transformer T1 and :50 the grid of thetube" V1, the latter circuit being commonly known as the grid circuitofthe tube.

The plate voltage of the tube V1 is supplied by battery B1 through theprimary winding of the transformer Tti The energy amplified by'the 66tube V1 impressed upon the grid of tube V2 which is of the rectifyingtype, the grid circuit of the latter tube including a battery B2 whichproduces the voltage for properly biasing the grid electrode of the tubewith respect to its cathode. The plate circuit of the tube V2 includesthe oathode of'the tube, both halves of the secondary winding oftransformer T2, the conductor common to these two halvesof the secondarywinding, the milliammeter MA, the resistors Z1, Z2, and Z3, the batteryB1 and the resistor .20. The battery B1 of this series circuit isemployed to supply the anode voltage for the rectifying tube V2. Theflow of anode current through the series circuit just described will beutilized for the operation of various relays as will now be described.

The resistors Z1, Z2 and Z3 are shunted by the windings of relays R1, R3and R3, respectively.-

These resistors may be of different magnitudes and the relays will be soadjusted that they will operate at different values of current flowingthrough the series anode circuit of tube V2, above described If thecurrent flowing in this series circuit is of very low value it may besufficient to produce a voltage across the resistor Z1 which is ample tooperate the relay R1. But this small current will produce voltagesacross resistors Z2 and Z3 which will be insufiicient to operate therelays R2 and R3. If a greater current is rectifled by the tube V2, thevoltage impressed across the resistor Z2 may be sufficient to operatethe relay R2 and therefore relay R2 will be operated. Inasmuch as thesame current traverses the resistor Z1, the relay R1 will be maintainedin operation. If a still greater current flows through the anode circuitof tube V2, the voltage established across resistors Z1, Z2, and Z2 maybe sufficiently large so as to cause the operation. of allthree relaysR1, R2 and R3 and of course relay R3 will then operate while relays R1and R2 will be maintained in their operated condition.

The operation of the relay R1 will in turn operate the relay R'1, thecircuit of the winding of relay R'1 including the battery B1, theresistor Z1 the winding of relay R'1, the armature and contact of relayR1 and the upper blade of switch arm of switch. S5.

S4. Similarly the operation of relay R2 will cause the operation ofrelay R'2, current then flowing over the circuit including battery B1,resistor Z12, the winding of relay R'2, the armature and contact ofrelay R2, and the upper blade of switch S1. Similarly the operation ofrelay R2 will cause the operation of relay R: as will be clearlyunderstood.

By opening switches S1 and S2 and closing switches S3 and S4 theoperator may light any one of the, lamps L1, L2 or L3 which areassociated with the relays R'1, R'2 and R'2, respectively. When theoperator moves the rotary switch S5 to its contact I, the lamp L1 willbe lighted, the circuit for lamp L1 including the secondary windingoftransformer T3, the movable arm of switch S5 and lamp L1. By moving thearm of switch S5 to its contact 2, the lamp L1 will be disconnected fromthe secondary winding of transformer T3 and extinguished and lamp L2will be connected to that winding through the Consequently the lamp L2will be illuminated. By further moving the arm of switch S5 to itscontact 3, the lamp L2 will be extinguished and the lamp L3 will then beilluminated. The lamps L1, L2 and L3 are preferably colored lamps, thelamp L1 for example being colored red, the lamp L2 amber and the lamp Lsgreen. These three lamps will be used to indicate instantly to thespeaker or operator what the approximate level of the energy impressedupon the transmitter TR may be, the lamp L1 indicating a low level ofimpressed energy, the lamp L2 a higher level and the lamp L3 a stillhigher level. Of course more than three lamps may be employed in thiscircuit arrangement as will be obvious to those skilled in the art.

Suppose now that the switches S1 and S2 are both closed so as to connectthe transmitter TR to the primary winding of the transformer T1 andsuppose also that the buzzer Y is unoperated and that no speech or otherenergy is impressed upon the transmitter TR. Under these circumstancesthe current fiowing in the anode circuit of the rectifying tube V2 andthrough the resistors Z1, Z2 and Z3 will be so low as to be inadequateto operate relays R1, R2 and R3. The relays R'1, R'2 and R's will alsobe unoperated and if the movable arm of switch S5 is on its contact 0,none of the lamps L1, L2 or L3 will be illuminated. If now the circuitof buzzer Y is completed and the buzzer is held approximately three feetfrom the transmitterTR, the energy impressed'upon the transmitter andamplified by tube V1 and rectified for tube V2 will be of rather lowvalue. This small amount of energy will, however produce a voltageacross resistor Z sufiicient to cause the operation of relay R1. Theoperation of relay R1 will in turn operate the relay of R'1 which inturn will cause the lamp L1 tobe lit. The circuit of lamp L1 willinclude the secondary Winding of transformer T3, the armature and backcontact of relay R'3, the armature and back contact of relay R'2, thearmature and make contact of relay R'1 and lamp L1. The lamps L2 and L3will of course remain unlit. The lamp L1, which is painted red assuggested above, will indicate to the operator that the level of energyimpressed upon the transmitter TR is insufficient for good signaltransmission over the telephone circuit, for example, to which thetransmitter TR may be connected.

If now the buzzer Y is moved closer to the transmitter TR the amplitudeof the current flowing through the anode circuit of the tube V2 wil besuch as to produce a sufficient voltage across resistor Z2 to operatethe relay R2. The operation of relay R2 will then cause the operation ofrelay R'2 and this in turn will cause the lamp L2 to be lit. The circuitof lamp L2 will include the secondary winding of transformer T3, thearmature and back contact of relay R'2, the armature and make contact ofrelay R'2 and the lamp L2. By opening the circuit of the back contact ofthe armature of relay R'2, the lamp L1 will become extinguished. Theillumination of the lamp L2 will, however, indicate to the operator thatthe level of energy impressed upon the transmitter TR is better thanbefore but this level of energy will still be insuflicient for goodsignal transmission.

If now the buzzer Y is moved still closer to the transmitter TR, i. e.,the buzzer is now positioned in approximately the normal position of atalkers lips close to the transmitter TR, the magnitude of the rectifiedcurrent flowing through the resistor Z3 will produce such a voltageacross its terminals as will be sufficient to operate the relay R3. Theoperation of the relay R3 will in turn operate the relay R: and this inturn will illuminate the green lamp, L2. The circuit of the lamp L3 willinclude the secondary winding of the transformer T3 and the armature andmake contact of relayRa However, upon the opening of the back contact ofrelay -R3,-it will be clear that the lamp L2 will become extinguishedThe illumination of the green lamp L3 will indicate to the operator thatthe level of the energy impress"ed upon the'transmitter I'R' issufiici'ent for good*transmission. This position of the buzzer Y withrespect to the transmitter TR may now approximate that whicha speakerslips should occupy for good transmission. If the buzzer Ybe now movedaway from the transmitter TR a sumcientdistance the relay Ra willrelease and this in turn will cause the relay 'Bl'sto release.

back contact of relay R's and the armature and make contact of relayR'2.

If the buzzer be now moved still further away from the transmitter TRthe relays R2 and R2 will become released and the lamp L2 extinguished.But if the flow of current through the resistor Z1 is sufficient tomaintain relay R1 operated relay R'1 will also remain operated and thenthe lamp L1 will become reilluminated.

Thus it will be clear that as energy similar to that obtained from. thebuzzer Y is impressed upon the transmitter TR, one of lamps L1, L2 or L3will be illuminated and remain illuminated depending upon the level ofenergy so impressed upon the transmitter. As the level of energy risesfrom a very low value to a much higher sively operated in sequence.

\ energy becomes reduced from a very large value to a very small valuethe lamps L3, L2 and L1 will i become progressively illuminated insequence.

Each of the lamps will indicate within reasonable limits the approximatelevel of the energy conveyed to the transmitter TR.

If the circuit of the buzzer Y be now opened and speech beimpressed'upon the transmitter TR the level of the currents flowingthrough the anode circuit of tube V2 and through resistors R1 and R2 andR3 will cause the lamps L L2 and L3 to become illuminated according tothe magnitude of the speech currents so impressed, as will be clear fromthe description given hereinabove. A loud tone produced, for example,quite close to the transmitter TR will cause the lamp L3 to becomeilluminated and then lamp L3 will remain illuminated if this rather loudtone persists. If the tone be produced somewhat more distantly from thetransmitter then the lamp Lz-the amber lampwill be illuminated and thelamp L2 will remain illuminated if this tone persists at approximatelythe same level. If the tone be very soft or very distant from thetransmitter TR then of course the lamp L1-the red lamp will be lighted.If the tone be unsteady the lamps will flash on and off according. tothe durations of the tone pulses, the frequency of the flashes dependingof course upon the nature of the words or phases used, as will beunderstood by those skilled in the art. Yet the average light impressionobtained from the various lamps, that is, the average time during whichthe green lamp L3 will be lit or the amber lamp L2 will be lit, etc.,will determine whether this speech is good or only fair or very poor. l

The tone impressed upon the transmitter TR tion ofvacuum tube amplifiercircuits.

described causes a variablecurrent to flow through theprimary winding ofthe transmitter T1, the normal carrier current being supplied bybatteryB1. This variable modulated current produces an alternating currentvoltageinthe secondary winding 'oftransformer T1 which is applied to thegrid circuit of the amplifiertube V1. The plate current of the tube V1is then caused to vary due to the alternating current voltage applied tothe grid according to the customary ac- The amplified alternatin currentvoltage transmitted tothe secondary winding of transformer T; will .thenbe applied to grid of the rectifying Jtube V2. The grid or thelatter'tube is biased negativelywith respect to its cathode: and hencewill pass-plate current only during the positive 'grid swings, and thenonly in accordance with the grid-voltage plate-current characteristiccurve of this tube. The rectified current of tube V2 will then flowthrough the resistors Z1, Z2 and Z3 as well as through the milliammeterMA and the voltages produced at the terminals of the latter resistorswill be employed to operate one or more of the relays R1, R2 and R3 asalready explained.

It will be apparent that the arrangement illustrated in the drawing maybe employed to visually indicate the proper and improper use of atelephone transmitter. The signals will especially indicate the properdistances; required between thelips of the speaker and the telephonetransmitter TR and/or the proper tone level for good transmission.

The apparatus described in this application may be readily employed forvarious purposes. The apparatus may be used for example, to train theannouncers and artists in broadcasting studios to talk or sing into themicrophone with the proper volume or voice level.

While this invention has been shown and in certain particularembodiments merely for the purpose of illustration, it will beunderstood that the general principles of this, invention may be appliedto other and widely varied organizations without departing from thespirit of the invention and the scope of the appended claims.

, What is claimed is:

l The combination of a telephone transmit- ,ter upon which speechcurrents may be impressed, an amplifier coupled to said transmitter,

a detector coupled to said amplifier, a plurality the correspondingindicator, and means for successively operating a predetermined numberof said relays, the number of relays operated corresponding to theamount of energy in the various frequency components impressed upon saidtransmitter.

2. Apparatus for indicating instantly the amount of energy impressedupon a telephone transmitter, comprising a detector for detectingsubstantially all of the components of the impressed energy, and meansresponsive to the detected energy for indicating the approximatemagnitude of the detected energy, said indicattude of the detectedenergy, and signal devices controlled by said relays.

. 3. A system for instantly indicating to a speaker the amount of energyimpressed upon a telephone transmitter, comprising means for detectingthe. energy impressed on the telephone transmitter, a plurality ofimpedances connected in series with said detecting means, first andsecond groups of relays, the windings of the relays of the first grouprespectively shunting said impedances, the relays of the second groupbeing operated in response to the corresponding relays of the firstgroup, means for successively operating a predetermined number of therelays of the first group, the number of relays operated correspondingto the amount of energy impressed upon the telephone transmitter, andindicating means controlled by the relays of the second group.

4. A system for instantly indicating the amount of energy impressed upona telephone transmitter, comprising means for detecting the energy insubstantially all of the components impressed upon said telephonetransmitter, and means responsive to the detected current for indicatingthe amount of detected current, said indicating means including aplurality of impedances connected in series with each other and withsaid detecting means, the detected current flowing through said seriesimpedances, a plurality'of relays, the windings of which respectivelyshunt said impedances, said relays operating successively, the number ofrelays operated correspondingto the magnitude of the detected current,and indicating means controlled by said relays.

- 1 JOHN J. SCHLUTER.

